Laboratory studies of successional patterns in assemblages of attached estuarine diatoms

Graduation date: 1973Successional patterns of attached estuarine diatoms were investigated\ud using laboratory model ecosystems. Artificial substrates\ud of acrylic plastic were exposed to 0, 4, and 10 hours of desiccation\ud per day. Diatom assemblages that developed under temperatures\ud normal for Yaquina Bay, Oregon (control ecosystem) were compared\ud to assemblages that developed at temperatures elevated 10 C (heated\ud ecosystem).\ud Continuously submerged substrates were quickly invaded by solitary,\ud motile and attached diatoms. By the end of the experiment,\ud filamentous and tube dwelling colonial diatoms had become established\ud with many motile and epiphytic diatoms interspersed among the colonies.\ud However, planktonic taxa were the first to settle on the substrates\ud exposed to 4 and 10 hours of desiccation. These taxa were\ud gradually replaced in prominence by solitary, motile and attached taxa\ud that had previously colonized the continuously submerged substrates\ud and by several species that were tolerant of desiccation and high air\ud temperatures. Again, filamentous and tube dwelling forms began to\ud establish colonies at the end of the experiment.\ud A total of 21,569 diatoms was counted in 42 samples, and 136\ud species were identified. The most abundant diatoms found in the\ud control ecosystem included Navicula directa, Thalassiosira no. 1,\ud Thalassionema nitzschioides, Nitzschia no. 2, and Navicula diserta.\ud Thalassiosira no. 1, Thalassionema nitzschioides, Nitzschia aerophila,\ud Nitzschia sigma, and Navicula no. 2 were the most abundant\ud species in the heated ecosystem. Of these taxa, Navicula directa\ud and Thalassionema nitzschioides were the most evenly distributed\ud over the samples. Species diversity was higher in the heated ecosystem\ud than in the control ecosystem